The principle of the electric motor/generator is shown here. During the braking recuperation, as in the vehicle generator, AC current is generated, however with a permanent magnetic field. If the AC/DC converter distributes the DC to the windings at the right time, the permanent magnet turns automatically.

Almost all manufacturers use the synchronous motor, because without collector and commutator, it has a particularly high efficiency. Inside of it a permanent magnet rotates.

Although, from the outside it looks like it's put together from simple metal-plate, it contains rare elements like neodymium and dysprosium.

Getting away from crude oil can also mean, having to depend on raw-materials which are only mined in a few countries (e.g., China) and are relatively rare. Apparently even their recycling is difficult. 09/10